glPixelZoom(3G) OpenGL Reference glPixelZoom(3G)
NAME
glPixelZoom - specify the pixel zoom factors
C SPECIFICATION
void glPixelZoom( GLfloat xfactor,
GLfloat yfactor )
PARAMETERS
xfactor, yfactor Specify the x and y zoom factors for pixel write
operations.
DESCRIPTION
glPixelZoom specifies values for the x and y zoom factors. Let, (x , y )
r r
be the current raster position, and let interlace be either 1 or 2
corresponding to whether GLINTERLACESGIX is enabled or not,
respectively. Then, during the execution of glDrawPixels or
glCopyPixels, for a pixel that is in the mth row and nth column of the
source image, the destination pixels that are candidate for replacement
are those whose centers are on the bottom or left edge of, or inside the
rectangle with corners at
(x + n x xfactor, y + m x interlace x yfactor) and
r r
(x + (n + 1) x xfactor,y + (m x interlace + 1) x yfactor)
r r
Pixel zoom factors are not limited to positive values. Negative zoom
factors reflect the resulting image about the current raster position.
ERRORS
GLINVALIDOPERATION is generated if glPixelZoom is executed between the
execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GLZOOMX
glGet with argument GLZOOMY
glGet with argument GLINTERLACESGIX
MACHINE DEPENDENCIES
The SGIXinterlace extension is supported only on InfiniteReality
systems, on RealityEngine, RealityEngine2, and VTX systems, and on O2
systems.
On InfiniteReality systems, the absolute values of the zoom factors must
be strictly less than 128. If not, they are clamped and GLINVALIDVALUE
is generated.
Pixel zoom factors are snapped to fixed point precision on O2 systems,
Indy and XL systems, XS, XZ, Elan, and Extreme systems. glGet will
return these values.
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glPixelZoom(3G) OpenGL Reference glPixelZoom(3G)
SEE ALSO
glCopyPixels, glEnable, glDrawPixels.
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